Psychosis in bipolar disorder: Does it represent a more "severe" illness?

OBJECTIVES: Although there is a common clinical assumption that bipolar disorder with psychotic features reflects greater severity than bipolar disorder without psychosis, the existing empirical literature is mixed. This study investigated the phenomenology of psychosis as well as demographic, clinical, functional, and neuropsychological features in a large, cross-sectional sample of participants with bipolar disorder divided by history of psychosis.
METHODS: In a large single study, 168 affective-only bipolar disorder (BP-A) participants and 213 bipolar disorder with a history of psychosis (BP-P) participants completed a comprehensive clinical diagnostic interview and neuropsychological testing. t tests, chi-square tests, and Bayes factors were used to investigate group differences or lack thereof.
RESULTS: The prevalence of psychosis in this sample (53%) was similar to published reports. Nearly half of BP-P participants experienced grandiose delusions, and relatively few endorsed "first-rank" hallucinations of running commentary or two or more voices conversing. There were no demographic or neuropsychological differences between groups. BP-A participants experienced greater chronicity of affective symptoms and a greater degree of rapid cycling than BP-P participants; there were no other clinical differences between groups.
CONCLUSIONS: Overall, these results contradict the conventional notion that bipolar disorder with psychotic features represents a more severe illness than bipolar disorder without a history of psychosis. The presence of psychosis does not appear to be associated with poorer clinical/functional outcome or suggest a greater degree of neuropsychological impairment; conversely, the absence of psychosis was associated with affective chronicity and rapid cycling. Nosological and treatment implications are discussed.